Medical organizations and experts on medical ethics yesterday expressed dismay at the Supreme Court's ruling barring the parents of Nancy Cruzan from withdrawing the feeding tube from their comatose daughter, saying it interferes with the ability of doctors to help patients and families to make life-or-death decisions.

At the same time, they applauded the fact that the court, in the first right-to-die case it has considered, concluded that an individual has a constitutional right to refuse medical treatment and that "treatment" can include food and water.

But because Nancy Cruzan, who was 25 when she suffered the accident that left her in a coma, never wrote down her wishes regarding medical care, the court agreed with the Missouri Supreme Court that her parents lacked "clear and convincing evidence" that she would have wanted her treatment stopped.

Medical experts said that standard puts an intolerable burden on patients and families in states, such as Missouri, New York and Illinois, which require such evidence before allowing the withdrawal of care.

"It's a devastating opinion," said D. Joanne Lynn, a medical ethicist and associate professor at George Washington University Medical School. "Most of us will face an illness that, at some point in time, will interrupt our competence and require that someone else make decisions for us. That someone now has their hands tied."

But organizations for handicapped people and antiabortion groups hailed the decision, saying it affirmed that the lives of patients who cannot speak for themselves are as valuable as the lives of those who can.

"No matter how profound a person's disabilities, he or she must not be deprived of the most basic care," said John Willke, president of the National Right to Life Committee.

The ruling means that the ability of doctors and family members to decide whether to withhold or withdraw treatment when a patient is comatose or terminally ill will vary enormously from state to state, depending on each state's laws and prior court decisions.

The District and more than 40 states, including Maryland and Virginia, have laws allowing patients to specify their wishes in advance or to designate someone to make medical decisions for them if they become incompetent. But many states specifically exclude the right to refuse food and water from provisions allowed in such "living wills." Experts estimate less than 5 percent of the adult population has a "living will."

The decision "leaves other states free to adopt less rigid rules" than Missouri, said John Pickering, a lawyer representing the American Academy of Neurology. "And this is where the battle must turn."

Representatives of the American Medical Association and other medical groups vowed yesterday to push for new state laws that give more authority to doctors and family members to make decisions for medically incompetent patients. They said the ruling will encourage more people to discuss their medical care wishes with doctors.

But experts said it may be difficult for people to write "living wills" specific enough to cover all contingencies. "I believe most people and most doctors still remain highly reluctant to talk about these matters," said Daniel Callahan, director of the Hastings Center for Medical Ethics.

Others predicted that a major impact of the decision will be to increase enormously the cost of prolonged care for patients such as Cruzan, who are comatose and unable to express their wishes. The state of Missouri is paying $130,000 a year for Cruzan's care.

Nancy Dickey, a trustee of the AMA, said under the Missouri law, it appears that hopelessly ill infants or mentally retarded patients, and all others not competent to make their own decisions apparently would have to be kept alive as long as possible, whatever the cost.

An option open to Cruzan's parents may be to move their daughter to another state, suggested Arthur Caplan, director of the Center for Biomedical Ethics at the University of Minnesota. Caplan called the ruling a "sad decision" that will frighten sick people and may prompt them to consider suicide before they lose control over their medical destinies.

"It puts us in a place where we're giving all sorts of care to people who don't want it, at public expense, when everyone agrees they wouldn't want to live that way anyway," he said.

Staff writer Erin Marcus contributed to this report.